entrench

Concise Oxford English Dictionary © 2008 Oxford University Press:
entrench/ɪnˈtrentʃ/

▶verb

• 1 establish so firmly that change is difficult: ageism is entrenched in our society.

  ■ apply extra legal safeguards to (a constitutional right guaranteed by legislation).

• 2 establish (a military force) in trenches or other fortified positions.

– derivatives
entrenchment noun.