I haven't heard of any medical patients being arrested for having concentrates.
The new law doesn't say anything about which solvents can be used for extraction, but the product label will need to say what was used.
But even now with legalization, non medical 21+ users are only allowed to have 5 grams of concentrate because of LD88. It would have been 2.5 oz of concentrate if LD88 wasn't an emergency bill. Med patients can still have 2.5 oz of concentrate.
https://legislature.maine.gov/legis/bills/bills_128th/chapters/PUBLIC1.asp
22-A. Marijuana concentrate. "Marijuana concentrate" means the resin extracted from any part of the plant genus cannabis and every compound, manufacture, salt, derivative, mixture or preparation from such resin, including hashish. In determining the weight of marijuana concentrate, the weight of any other ingredient combined with marijuana to prepare a marijuana product may not be included.
1. Person 21 years of age or older. A person 21 years of age or older may:
A. Use, possess or transport marijuana accessories and use, possess or transport up to 2 1/2 ounces of prepared marijuana or a combination of marijuana and marijuana concentrate, which may include
no more than 5 grams of marijuana concentrate;
B. Transfer or furnish, without remuneration, up to 2 1/2 ounces of marijuana or a combination of marijuana and marijuana concentrate, which may include no more than
5 grams of marijuana concentrate, and up to 6 immature plants or seedlings to a person who is 21 years of age or older;