The spec
http://java.sun.com/j2se/1.4.2/docs/api/java/awt/doc-files/FocusSpec.html#RequestingFocus

Says:
"The request will also be denied if the Component's top-level Window is not the focused Window and the platform does not support requesting focus across Windows."

This assertion is not satisfied on Solaris (not supporting cross window focus transfer) and JDK6 reference implementation.
The following JCK tests (imported from PP TCK) fail due to this:

api/java_awt/awt_focus_subsystem/requesting_focus/index.html#RequestFocus[RequestFocus_hw_0004]
api/java_awt/awt_focus_subsystem/requesting_focus/index.html#RequestFocus[RequestFocus_lw_0004]
JCK: 7b08
JDK: 6b105
Platform: Solaris


Please see the following minimized test 
(for simplicity delays were inserted instead of more complex verifications in the original test cases)

---
import java.awt.*;
import java.awt.event.FocusListener;
import java.awt.event.FocusEvent;

public class CrossWindowFocusTransferBug {

    /**
     * Precondition: two components are in different frames:
     * firstFrame and secondFrame. secondComponent in secondFrame is the current focus owner.
     * <p/>
     * The test expects:
     * - firstComponent's request will be denied if the platform does not support
     * requesting focus across window
     */
    public static void main(String[] args) throws InterruptedException {

        Frame secondFrame = new Frame();
        Component firstComp = new Button();
        Component secondComp = new TextField();

        Frame firstFrame;
        firstFrame = new Frame();
        firstFrame.setLayout(new FlowLayout());
        firstFrame.setLocation(50, 50);
        firstFrame.setVisible(true);
        Thread.sleep(1000);
        firstFrame.add(firstComp);

        //focus the second frame

        secondFrame.setVisible(true);
        secondFrame.toFront();
        Thread.sleep(1000);
        System.out.println("second frame has focus: " + secondFrame.hasFocus());
        System.out.println("first frame has focus: " + firstFrame.hasFocus());

        secondComp.addFocusListener(new FocusListener() {
            public void focusGained(FocusEvent e) {
                System.out.println("second component gained the focus. It's OK");
            }

            public void focusLost(FocusEvent e) {
            }
        });

        secondFrame.add(secondComp);
        System.out.println("requesting focus for the second component...");
        secondComp.requestFocus();
        Thread.sleep(1000);

        //start tracking the other component in another window
        firstComp.addFocusListener(new FocusListener() {
            public void focusGained(FocusEvent e) {
                System.out.println("first component gained the focus" +
                        " when its top-level window is not the " +
                        "focused window and platform does not " +
                        "support requesting focus across window. It's NOT OK");
            }

            public void focusLost(FocusEvent e) {
            }
        });
        System.out.println("requesting focus for the first component...");
        firstComp.requestFocus();
        Thread.sleep(2000);

        firstFrame.dispose();
        secondFrame.dispose();

    }

} 
---