The laws regarding asking for proof of vaccination vary by country and jurisdiction. In some countries, such as the United States and Canada, businesses and employers are generally allowed to ask for proof of vaccination as a condition of entry or employment, although there are some exceptions and limitations.
In the United States, for example, the Equal Employment Opportunity Commission (EEOC) has stated that employers may require employees to be vaccinated against COVID-19 as long as they comply with certain legal requirements, such as providing reasonable accommodations for employees who are unable to be vaccinated due to a disability or religious belief. However, some states have passed laws that restrict or prohibit requiring proof of vaccination for certain purposes, such as attending school or entering public buildings.
In Canada, the federal government has stated that it will not require vaccine passports for domestic travel or entry to federal buildings, but some provinces and territories may have their own rules or guidelines for businesses and organizations regarding proof of vaccination.
It is important to research the laws and guidelines in your specific jurisdiction and comply with all applicable regulations when asking for or providing proof of vaccination.