The owner's rights
The owner of the land that supports the easement does not have the right to make it more difficult to pass on his land. However, nothing prevents him from installing a gate, as long as the gate does not make it more difficult to use the easement. For example, he must give me the keys or the "beeper" if the gate is automated.
Everything depends on the circumstances: if the gate does not hinder the use of the easement, it can be installed. On the other hand, if it causes a significant disturbance, as the beneficiary of the right of way, you can ask the owner to remove it. In the event of a dispute, the judge will assess the situation and make a decision based on the elements presented to him.