Technically the word "régime
" refers to any system of control, or more specifically a system of government
, but in English language
it has become a largely pejorative synonym
" or "administration
", implying moral disapproval and/or political opposition.
Thus one can speak of "the vicious oppressive régime of Borduria"; but seldom of "the régime in Washington" or of "the current Blair régime".
Compare: Ancien régime, Bush régime, Vichy régime, régime change