You do not have to accept the clearance.

.... and you could be sitting on the ground forever waiting for a better one.
This is actually quite common in the NY/CT area. Freezing level at 4000,
overcast at 2000, I filed for 3000, and got 7000 despite comments to the effect
that I can't accept routings into icing conditions and need to stay below the
freezing level.

We negotiated on the ground for an hour. Their alternative was either 7000 and
their routing, or come back tomorrow. They were not going to give me anything
else for any reason.

So, I accepted the clearance and negotiated in the air. Picking up ice at
7000, I was able to get 8000 and break out on top.

With this in mind, to reject the clearance because it happens to be the same as
a SID won't get you far. At least not in this town. You fly what they want,
or you don't fly.

Jose



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