I can not speak for MD rules. In Virginia state code allows one to use a dip net, hand lines, and two crab pots to catch up to one Bu of crabs per day. The limit is per vessel if fishing from a vessel. Crab Traps, i.e. something that a crab can enter and exit at will until closed, are considered to be the same as hand lines with no limitations.
If you want to use a trot line you have to have a license.
If you want to use more than two crab pots per person you can get a license for up to 5 crab pots.
There are restrictions regarding setting crab pots in marked channels (all Rudee inlet is considered a channel) and in the deep water sanctuary which amounts to most all of the main stem of the bay more than 30 feet deep, and the ocean waters off of Virginia Beach. The lower bay sanctuary which basically goes from Ocean View Pier, to Thimbal Shoals Light to Cape Charles (the cape not the town), to Cape Henry and back to Ocean View Pier is closed during the summer to commercial crabbing but not recreational crabbing.
The MD/VA/PRFC reciprocity agreement only talks about fishing licenses and fishing. Nothing in it talks about crabbing licenses. For a full text of the agreement click on the link provided below.http://www.mrc.state.va.us/regulations/Reciprocity_Agreement_2011.pdf