url(r"^(?P<slug>[\w\-]+)/apply/$", "team_apply", name="team_apply"),

def can_apply(team, user):

    state = team.get_state_for_user(user)

    if team.access == "application" and state is None:

        return True

    else:

        return False

        "can_apply": can_apply(team, request.user),

@login_required

def team_apply(request, slug):

    team = get_object_or_404(Team, slug=slug)

    state = team.get_state_for_user(request.user)

    if team.access == "invitation" and state is None:

        raise Http404()

    if can_apply(team, request.user) and request.method == "POST":

        membership, created = Membership.objects.get_or_create(team=team, user=request.user)

        membership.state = "applied"

        membership.save()

        # contrib.message

        return redirect("team_detail", slug=slug)

    else:

        return redirect("team_detail", slug=slug)

    {% if can_apply %}

        <form method="post" action="{% url team_apply team.slug %}">

            {% csrf_token %}

            <input type="submit" class="btn btn-primary" value="apply">

        </form>

    {% endif %}