The phrase "a convenient justification for" is correct and usable in written English.
It can be used when discussing a rationale or reasoning that is easy or advantageous for a particular action or decision.
Example: "The company presented a convenient justification for the layoffs, claiming it was necessary for financial stability."
Alternatives: "an easy excuse for" or "a handy rationale for".
One can only hope that they are using the attacks as a convenient justification for a decision that was already taken.
The casting of Caribs as not-really-indigenous served as a convenient justification for colonial aggression against them and their forced removal from their homelands.
This might be a convenient justification for not engaging in the transfer of skills, and thus avoiding the necessary mending of cross-cultural barriers as well as the shedding of the mutually shared misanthropic perceptions.
After all, in the end, by hook, crook, or secret "law," they will find a convenient justification for doing just what they want to do anyway.
Even if it were feasible for one country to bear such a burden, such interference can ultimately be justified only in cases of self-defence, and for one state to intervene in another's affairs on any other grounds merely provides stronger states with a convenient justification to bully the weaker, and thereby becomes a recipe for international instability.
While the rising temperature is dismissed by global warming naysayers as part of Earth's natural cycle, there is no convenient justification for the rate of deforestation that's occurring all across the globe.
Slavish devotion to market theories serves as a convenient rational justification for some to take selfish actions they know to be wrong or questionable.
The five-man majority rationalized their ruling as being necessary for safety, security and efficiency, the government's overused and all-too-convenient justifications for its steady erosion of our freedoms since 9/11.
Although the conservative Nationalist generals were already in the advanced stages of a planned uprising, the event provided a catalyst and convenient public justification for their coup.
