Yes. 100% legal.
Under the First Amendment of the United States Constitution, your ordination is recognized as legal in all 50 States.
Laws and protocols regarding officiating weddings and performing other ceremonies will vary based on your location.
In the United States and in many countries worldwide, ULC ministers are authorized to officiate weddings, commitment ceremonies, funerals, baptisms, naming ceremonies, hold services and all other sacraments and rites regularly performed by ordained clergy as part of the belief system the minister represents. Ministers in the ULC are authorized to ordain others as ministers, and are also authorized also start their own congregations.
If you were asked to officiate a wedding, you can verify the current requirements to perform a wedding with your County Clerk’s Office and/or the County Clerk’s Office in the city a wedding will be performed in.