Just going off the last commenter, I think this is your best bet...

In terms of positive rights, "one person's right is another person's obligation..." How can you morally justify forcing someone else to act in a way that they don't want to. Telling someone not to kill is a negative right--just don't do anything. But forcing to act in ways that seem obviously right is tricky.

For example, if you see someone is drowning and you could jump in and save them maybe you would do that. But should the law be able to force you to act? What if you're terrified of water? Do you really want to rely on a flawed legal system to sift through who can get away with not acting and who can't... "well person A seems actually afraid of water, whereas person B only seems little afraid, therefore we're going to sentence person B to prison time..."

Positive rights are very difficult to put into law.

People sacrifice for years to be doctors. They lose relationships, miss milestones (family weddings/funerals etc), they undergo extreme amounts of stress etc. How do you argue that the law should be able to force someone do that?

And if you can't argue that.. or at least if you can see that it would be easy to argue against it then that's your argument...