the.com/loophole

means A gap or ambiguity in a law, rule, or contract that lets someone legally do what the rule was meant to prevent.

from Literally a narrow slit cut into a castle or fortress wall — wide enough to shoot an arrow or peer out through, too narrow for an enemy to climb back in through. By the 1600s, 'loophole' had widened figuratively into any narrow means of escape, and by the 1700s it had settled into its modern sense: a slender gap in the wording of a law or rule, just wide enough for someone determined to slip through it.