open season

Short definition from Wiktionary

Noun

1. 1
   A period of time during the calendar year when authorities within a jurisdiction permit the unrestricted hunting of one or more kinds of animal wildlife.
2. 2
   A situation in which someone is endangered, blamed, harassed, or opposed in a sustained manner by a number of others; a situation in which something is endangered or otherwise opposed.
3. 3
   A situation or period in which some activity is routinely carried on.