Once you're served a notice to appear in mobilization center - yes, it is illegal to not comply. If you're not served one - there should be no repercussions. H

Once you're served a notice to appear in mobilization center - yes, it is illegal to not comply. If you're not served one - there should be no repercussions. However, you may be required to stay in your home town and not travel outside without permission if you are potentially subject to mobilization (which is the case for ~50% of men in Russia) - IANAL, there's different readings of the rules here.