You were probably sent here by a page saying that your state regulates something called field investigation or field archaeology, and that the phrase covers more than it sounds like it does. It does. This page explains how much more.
Most states that say anything about detecting regulate what you do to the ground: digging, removing, disturbing. Three states in this directory regulate something else. They regulate the search, and they define the search by what you were looking for.
That inverts the usual advice completely.
The one thing to take away
Here the rule bites before you dig. In two of the three it bites before you switch on.
So the decision point is not the signal and not the hole. It is the car park. The question the law asks is not what you did but what you came for, and that is a question you have already answered by the time you walk through the gate.
The practical consequence is the uncomfortable one: you cannot fix it afterwards by not digging. In a state that reaches the activity, declining to recover a find does not undo the entry. There is no cautious version of the conduct available once you are on the ground with the wrong purpose. The decision has to be made before you arrive.
The question that sorts any state
Ask it of the defined term, never the section heading:
Does the operative verb describe what you do to the ground, or what you were looking for when you walked onto it?
Headings are written by publishers and they mislead in both directions. Wisconsin's section is headed "Field archaeology", which reads like professional licensing and is what caused this project to file Wisconsin in the wrong group the first time. The definition is what settled it.
Massachusetts: the broadest, and the only one with no site requirement
Operative text, M.G.L. c. 9, 27C:
"No person, corporation, agency or authority of the commonwealth or any of its political subdivisions shall conduct field investigation activities on any land owned or controlled by the commonwealth, its agencies or political subdivisions or on any historic or archeological landmarks or on any lands restricted by section thirty-one of chapter one hundred and eighty-four of the General Laws without first securing a permit from the state archeologist."
The definition is what makes this different. 950 CMR 70.04:
"Field Investigation means the study of traces of human culture or other remains of any land or water site by means of surveying, digging, sampling, excavating or removing surface or subsurface objects, or the entrance onto a site with that intent."
Read plainly: walking into a municipal park intending to dig up traces of human culture is itself the regulated act. Nothing has to be found, and nothing has to be damaged.
And unlike the other two states on this page, Massachusetts has no requirement that the land be an archaeological site. 950 CMR 70.03(1) says the permit is needed where the investigation will be "located on state, county or municipal property", full stop. Every town common in the Commonwealth is in scope.
Penalty, 950 CMR 70.30(1): a misdemeanour, a fine of up to $500 or up to six months' imprisonment. And 950 CMR 70.03(2): "All specimens collected through field investigation activities conducted under permit as provided in 950 CMR 70.00 shall be the property of the Commonwealth." So the permit route does not give you your finds either.
What limits it, and this is the part to get right
The defined term is the study of "traces of human culture or other remains".
Sweeping a town beach for dropped modern coins and jewellery is not the study of traces of human culture. Reading this rule as a ban on that would be wrong, and it would be wrong in the direction that sends a lawful detectorist home.
Relic hunting on municipal ground is squarely inside the definition.
The line is the searcher's object. It is the same kind of line as New Mexico's word "knowingly", and it is drawn by your purpose rather than by the land or the equipment.
What you do differently in Massachusetts: decide which of those two activities you are doing, before you go, and be able to say so. If you are looking for modern losses on a beach, you are outside the definition. If you are looking for anything older, on any public land in the state including a town park, you need a permit from the State Archeologist first.
Two things we have not resolved, and will not paper over
1. Does a non-destructive sweep need a permit at all? Secondary sources say non-destructive field investigations need only written notice to the State Archeologist rather than a permit. That carve-out is not in 950 CMR 70.00 as published. 70.20 is headed "Exceptions" and is entirely about human skeletal remains. The regulation does distinguish Destructive from Non-Destructive in the 70.04 definition, and lists "magnetometer studies … and other remote sensing studies" as Non-Destructive methods. But the permit requirement in 70.03(1) sentence one is not limited to Destructive investigations, and only sentence two is. Whether a sweep with no digging needs a permit turns on reading those two sentences together, and that is a question for the Massachusetts Historical Commission rather than one for us to settle on this page. We have not established where the notice-only rule comes from in any primary source.
2. A defect in the statute itself. M.G.L. c. 9, 27 requires a permit for "a field investigation, as defined in section twenty-six A". Section 26A as it currently stands contains no definition of the term; it is a list of the State Archeologist's duties, and section 26 does not define it either. The only definition in force is the regulatory one at 950 CMR 70.04, which is why this page quotes that and cites 27C for the prohibition. We do not reproduce the broken cross-reference as though it worked.
Wisconsin: the same definition, bounded to archaeological sites
Wis. Stat. 44.47(2):
"UNLICENSED FIELD ARCHAEOLOGY PROHIBITED. No person other than the state archaeologist and individuals licensed by the director may engage in any field archaeology on any state site or site owned by a political subdivision."
Definition, 44.47(1)(d):
"'Field archaeology' means the study of the traces of human culture by means of surveying, digging, sampling, excavating or removing objects."
That is the Massachusetts definition minus one clause. It is not a coincidence of drafting; it is the same instrument in two states. But the missing clause matters, and so does the land.
Two differences from Massachusetts, and neither should be smoothed over:
- Land. Wisconsin reaches only archaeological sites owned by a political subdivision, defined at 44.47(1)(b) as land with "objects or other evidence of archaeological interest". An ordinary municipal ballfield is not reached at all.
- Entry. Wisconsin has no "entrance with that intent" clause. It requires actually surveying, digging, sampling, excavating or removing. A Wisconsin detectorist who walks onto a local site and switches on has not yet engaged in field archaeology. Surveying it arguably starts the moment the coil moves. The permit routes back through the city, 44.47(4)(a):
"The director may not issue a permit for field archaeology on a site owned by a political subdivision without the written approval of the political subdivision which owns the site. No state agency or political subdivision may withhold that approval without good cause."
Wisconsin is the only state in this project where the municipality has a statutory say over a state permit.
Penalty, 44.47(7)(a)1: a forfeiture of not less than $100 nor more than $500 for unlicensed field archaeology, rising steeply for intentional damage or for removal for commercial gain.
Minnesota: Wisconsin's land reach with Massachusetts' entry clause
Minn. Stat. 138.33:
"No person, including state or other public employees other than the state archaeologist and individuals duly licensed by the director of the Minnesota Historical Society shall engage in any field archaeology on any state site."
Definition, 138.31 subd. 7:
"'Field archaeology' means the study of the traces of human culture at any land or water site by means of surveying, digging, sampling, excavating, or removing objects, or going on a site with that intent."
So Minnesota has the intent clause that Wisconsin lacks. It bites at entry, like Massachusetts.
But "state site" is not what it sounds like. 138.31 subd. 14:
"'State site' or 'state archaeological site' means a land or water area, owned or leased by or subject to the paramount right of the state, county, township, or municipality where there are objects or other evidence of archaeological interest. This term includes all aboriginal mounds and earthworks, ancient burial grounds, prehistoric ruins, historical remains, and other archaeological features on state land or on land subject to the paramount rights of the state. Historical remains do not include bottles or ceramics manufactured after 1875."
Two things there. A "state site" includes a city's archaeological site, despite the name. And the definition carries a date cutoff you can actually use: bottles and ceramics made after 1875 are not historical remains for this Act.
Penalty, 138.41 subd. 1: a gross misdemeanour, and it requires a wilful violation.
What you do differently in Minnesota: the reach is to archaeological sites only, as in Wisconsin, but the trigger is entry with intent, as in Massachusetts. So on a Minnesota city park with no evidence of archaeological interest, this Act does not touch you. On one that has such evidence, you are inside it before you switch on.
Note separately that Minnesota state parks are governed by a different instrument, Minn. R. 6100.0900 subp. 2(F), which permits detector use only to find a specific item of lost property, with the park manager's prior written permission and under supervision. That is on the Minnesota page.
A trap in two of the three: the recreational-use clause
Both Wisconsin and Minnesota carry a clause that looks like reassurance. Both of them say "state property", and neither says municipal.
Wis. Stat. 44.47, preamble:
"This section is not intended to burden persons who wish to use state public property for recreational and other lawful purposes or to unnecessarily restrict the use of state public property."
Minn. Stat. 138.40 subd. 1:
"sections 138.31 to 138.42 are not meant to burden persons who wish to use state property for recreational and other lawful purposes or to unnecessarily restrict the use of state property."
Each says it twice, and each means state land. If someone quotes one of these clauses to you as reassurance about a city park, they have given you a sentence that does not address your land. The clause is worth knowing and it is worth knowing what it covers.
Summary
| Massachusetts | Wisconsin | Minnesota | |
|---|---|---|---|
| Instrument | M.G.L. c. 9, 27C; 950 CMR 70.00 | Wis. Stat. 44.47 | Minn. Stat. 138.31 to 138.42 |
| Land | All state, county and municipal property | Archaeological sites owned by the state or a political subdivision | Archaeological sites owned by the state, a county, township or municipality |
| Bites at entry? | Yes – "the entrance onto a site with that intent" | No – requires surveying, digging, sampling, excavating or removing | Yes – "going on a site with that intent" |
| Needs an archaeological site? | No | Yes | Yes |
| Penalty | Misdemeanour, up to $500 or 6 months | Forfeiture $100 to $500 | Gross misdemeanour, wilful only |
| Finds | Specimens taken under permit are the Commonwealth's | Title reserved on state sites, silent on local sites | Reaches objects and data belonging to the state |
None of these three statutes contains the words "metal detector". All three can reach a metal detectorist, and in two of them you are inside the rule before the machine is on.
Two of the three states do have a separate rule that names detectors, and it covers different land. Massachusetts has 302 CMR 12.04(12), the DCR parks and recreation rule: detectors may be used on coastal and inland sandy beaches, and elsewhere on DCR land only with staff permission and only to look for lost personal property. Minnesota has Minn. R. 6100.0900 subp. 2(F), quoted above. Both reach the state agency's own land, not municipal land. Wisconsin has no detector rule at all; 44.47 is the whole of its answer.
So in Massachusetts and Minnesota the question "which instrument applies" is decided by whose land you are standing on, exactly as it is for the states in you may sweep, you may not take.
Where these quotations come from
Every statutory and regulatory quotation on this page is reproduced from the state entry it belongs to, and each of those entries records what it was read from, which edition, and on what date. Follow the state link for that sentence.
Massachusetts was read from the published CMR and the consolidated General Laws; Wisconsin from the chapter 44 PDF at docs.legis.wisconsin.gov, the 2023-24 Wisconsin Statutes published and certified under s. 35.18 on 4 September 2026; Minnesota from the 2025 Minnesota Statutes published by the Revisor of Statutes, checked 21 September 2026.
One sourcing limit worth stating here rather than leaving on one page. The Massachusetts entry for 302 CMR 12.00 depends on a PDF that mass.gov now serves in a corrupted form, so that chapter could not be re-verified at source in October 2026. A request for the current text is outstanding with the Department of Conservation and Recreation and with the Secretary of the Commonwealth's State Publications and Regulations Division. It does not affect the field investigation material on this page, which comes from M.G.L. c. 9 and 950 CMR 70.00.