It probably is not illegal where you are, but there are different forms of "legalization" that may be used to "legitimize" bitcoin.  Two of the more important of these are "Legal Tender" and "Lawful Money".  Legalizing in this sense just means that you apply a pre-existing body of law to it.  It is already legalized in many ways everywhere.  If you break a law using bitcoin it is probably going to bring just as much trouble as if you used some other thing to trade, so it is legalized in that sense already everywhere.


The OP does not specify their country.  Each one presents different challenges, however as soon as the first nation state with an international exchange recognizes Bitcoin as a "legal tender" then all other countries that do exchange with this country also defacto recognize it as lawful.

Legal Tender law is a horrible thing and has resulted in tragic tyranny through out its history.  Under the banner of 'standardization' it has primarily been used to force a constituent population to accept something valueless as if it had value.
In the USA there have been great legal battles as to whether a paper currency that was not backed by specie (precious metal) could be deemed legal tender.  The battle was lost most everywhere and LT law constitutes an unlawful taking from the people by their government, degrades that government away from solid metrics of value for their economy and thereby sows the seeds for financial ruin deep into the national soils.

Bitcoin may be the answer to this for any nation member of the world bank that deems it to be a Legal Tender in their jurisdiction, no matter how small it be.  The first nation to do this will win the jurisprudential lottery forevermore, and the last one to do so will lose.

Legal Tender law is a horrible piece of government, but the best governments are those that also govern the government, itself and force it to do good for its people.  By this mechanism of making Bitcoin a Legal Tender, the Legasy of Legal Tender law may redeem itself by bringing solid metrics back to government standards everywhere.

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Another designation is "Lawful Money".  Jurisdictions that have this designation use it to categorize monetary forms that "may be accepted lawfully".
Legal Tender designates monetary forms that the government REQUIRES its citizens to accept for settlement of a debt.

One is allowed (but may be refused), the other is allowed and may not be refused (but in most jurisdictions you may also accept any other currency by contract, such as bitcoin).