If it is a legally recorded "easement" over someone else's property to gain access to your property - they MAY erect a gate providing they furnish you with a key or access code to continue to allow...
Depends where in the world you are.
In the UK and Australia the servient tenant has a much better hand than servient tenants in the USA where the common law has developed differently.
An easement is a property right, and unauthorized blocking of your easement is a trespass. You can have the blockage removed by court order, if necessary. Local law enforcement is often...
The language in the document that created the easement must be reviewed by a legal professional. For this type of situation you need to consult with an attorney who can review the situation and...