A protest has been held after campaign group A Woman's Place held a meeting in Cardiff.
The group, which campaigns on plans to change the law on gender recognition, had been due to host the event at the Mercure Hotel on Thursday.
But the hotel cancelled the event after safety concerns for guests, sparking a row and leading to the meeting being held at a secret location.
Pride Cymru and Wales Equality Alliance held a protest outside the museum.
A Woman's Place UK says it wants "respectful and evidence-based discussion" on changes to the Gender Recognition Act.
This includes a proposal that individuals can self-declare their gender without the need for medical evidence or proof as people currently have to apply for a certificate.
Members say they are concerned any changes would impact on women's only services and spaces.
A spokesperson for the Mecure hotel said: "The decision to cancel an event... was taken in the best interests of hotel guests and staff after concerns were raised about their safety, which is our priority, due to potential disruption and protests.
"The decision in no way implied any judgement on the views of those organising the event, or those protesting against it."