Entries Field Type Validation
Relational field validation (entries, assets, tags, users, etc.) works the same on the front-end as any other custom field would.

So if you have an Entries field with a handle houseCollege on an entry and it's marked as required and there is nothing submitted on the front-end for it, then using the error macro you mentioned:

{% macro errorList(errors) %}
    {% if errors %}
        &lt;ul class="errors"&gt;
            {% for error in errors %}
                &lt;li&gt;{{ error }}&lt;/li&gt;
            {% endfor %}
        &lt;/ul&gt;
    {% endif %}
{% endmacro %}


You would display any validation errors for that houseCollege field with:

{% if entry is defined %}
    {{ errorList(entry.getErrors('houseCollege')) }}
{% endif %}


And in the case of a missing required field, you'd get:

House College cannot be blank.