Given are the following two JPA entities:

@Entity
public class Event {

	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	@Access(AccessType.PROPERTY)
	private Long id;

	@ElementCollection
	private Set<Tag> tags;
}

@Embeddable
public class Tag {

	@Column(nullable = false)
	private String value;

}

It seems that Hibernate disregards the @Column(nullable = false) annotation on Tag.value if and only if Event.id is annotated with @Access(AccessType.PROPERTY).

I published a minimal test case on https://github.com/bwaldvogel/hibernate-element-collection-access-type-issue.
EventTest.testPersistInvalidTag() fails on the assertion (unexpected) if and only if @Access(AccessType.PROPERTY) is used on Event.id.