The “short” of it is… if you are a Clark County resident and you own or have in your possession a firearm capable of being concealed, you are required to register that firearm with the Las Vegas Metropolitan Police Department. Carrying such a firearm in Clark County without such registration is a violation of Clark County Code 12.04.200. Here is the code and the penalty for violating it.
12.04.200 - Registration of firearms capable of being concealed.
It is unlawful for any person with at least sixty days of residency in the county to own or
have in his possession, within the unincorporated area of Clark County, a pistol or other firearm capable of being concealed, unless the same has first been registered with the sheriff or with a police department of any of the incorporated cities of Clark County.
12.04.220 - Penalty for violation of Sections 12.
04.010—12.04.210. Any person who violates any of the provisions of Sections
12.04.010 through
12.04.210 is guilty of a misdemeanor and upon conviction shall be punished by imprisonment in the county jail for a term not to exceed six months or by a fine of not to exceed five hundred dollars, or by both.
I would suggest if you are worried about “legality,” that you take the firearm down to a police station and get it registered per the County code. Don’t think they will ask you anything about how long you may have been in possession of the firearm… but who knows. Anyway, the firearm is not “illegal” (assuming it was purchased legally by whomever, etc. and has not been used in the commission of a crime or crimes). The only thing perhaps “illegal” here is that it has been “possessed” by a Clark County resident without the appropriate registration required by Clark County Code 12.04.200.
Oh, and by the way, by the title of your post, you have given the whole of Nevada a bad time. The state of Nevada and all its County Governments,with the exception of Clark County, have NO gun registration requirements.