Crazy,
For the take-off and landing phases; most regulations derive from the ICAO Annex 6 – Operational Standard, which (slightly amended) goes like this:
States take this objective requirement, put in into their code, and publish it as regulations.
For the en-route phase of flight; most regulations are in compliance with the Standard of ICAO Annex 2 – Rules of the Air, which specify (apart from the take-off and landing phases) that an aircraft be flown at a height of 1000ft over built up areas and 500’ elsewhere. (It is difficult to fly into wires when at 500' AGL.)
In the UK (for those who operate to JAR-OPS 3); performance regulations are contained within the Subparts F, G, H and I and overall statement in the requirement for operational procedures in Subpart (D). The Rules of the Air are not prescribed in JAR-OPS, being one of the areas that is left to the individual States (i.e. rules are not harmonised).
If you are interested in a comprehensive debate on the take-off and landing phases, you might wish to visit the recent thread on Category A procedures found
here. Whilst this does not specifically refer to avoiding wires, it is covered in the discussion on a safe-forced-landing and exposure.