http://decision.tcc-cci.gc.ca/tcc-cci/decisions/en/item/71802/index.do 
Mills v. The Queen (May 21, 2014 – 2014 TCC 153) was a case where a taxpayer was ordered to pay to his ex-wife the full costs of child support even though the children were with him roughly half the time. He sought unsuccessfully to vary that order. In doing so he incurred costs of approximately $42,000 which he sought to deduct. When that deduction was disallowed he appealed to the Tax Court.
The court was sympathetic to his plight but found that it was bound by precedent to deny his appeal:
[20] I have much sympathy for Mr. Mills. I agree with him that it is not right that a parent who incurs legal expenses in order to obtain child support is entitled to deduct the legal expenses from income whereas the parent who incurs legal expenses in order to prevent child support from being established or increased or to decrease or terminate child support cannot deduct these legal expenses from income. Such a result is unjust, unfair and inequitable. In my opinion both parents should have the right to deduct legal expenses in such circumstances or neither one should.
…
[22] If I could provide Mr. Mills with some relief, I would do so. However, the position argued by Mr. Mills goes contrary to the weight of a strong body of jurisprudence. The principle of law that a payer cannot deduct legal fees incurred to prevent child support from being established or increased, or to have child support decreased or terminated, is so well entrenched that only Parliament can bring about legislative changes to the law. The fact that Parliament has not done so speaks to the will of our law-makers.
As a result the appeal was dismissed.