make a federal case of
Also, make a big deal of. Give undue importance to an issue, as in I'll pay you back next week—you needn't make a federal case of it, or Jack is making a big deal of filling out his passport application. The first hyperbolic expression, almost always used in a negative context, alludes to taking a legal action before a high (federal) court. The second alludes to an important business transaction (see big deal, def. 1).