Enforce

verb

1. To keep up, impose or bring into effect something, not necessarily by force.

   "The police are there to enforce the law."

2. To give strength or force to; to affirm, to emphasize.

   "The victim was able to enforce his evidence against the alleged perpetrator."

3. To strengthen (a castle, town etc.) with extra troops, fortifications etc.
4. To intensify, make stronger, add force to.
5. To exert oneself, to try hard.